This invention relates generally to open stackable platform trays for storing drawing sheets, paper stock, and the like.
Various types of platform trays are known to the art, and are used as an alternative to flat files, tubes, lockers, and vertical slat cabinets for storing large drawings sheets, paper stock, and the like in a flat, generally horizontal planar orientation.
One type of stackable modular interlocking tray utilizing molded plastic body with steel reinforcing is known, and has been marketed under the name of Sort-A-System.TM. by the Fidelity Products Company. Each Sort-A-System.TM. tray was capable of holding paper sheets having dimensions up to 26" by 393/4", and provided an open front through which the paper sheets could be removed or replaced.
However, the Sort-A-System.TM. trays present significant limitations. Despite the steel reinforcement, the trays cannot support a large volume of paper stock without bending or collapsing. The trays are limited to a smaller and non-standard sized paper sheet, while most paper stocks are obtained and maintained in sizes up to 42" by 32". The rear and sides of the Sort-A-System.TM. trays are generally open, which permits dust to build up on paper stock if left unused for a significant time, and which can expose the paper stock to uneven or inconsistent light and cause bleaching or discoloration of portions of the stock. Moreover, the legs of the Sort-A-System.TM. trays used to interlock trays stacked in a column are formed separately from the tray bodies and affixed to the tray bodies during assembly, thus producing projections that extend outwardly from the lines of the trays and create obstacles to working around the column of trays, create weak points where the legs could separate from the tray bodies and be damaged, and also producing visual discontinuity and a less aesthetically pleasing appearance.
The weight of a volume of paper stock can be difficult to calculate unless the particular type of paper stock is designated. For example, a text paper may be termed a "basis 24" with a size of 17" by 22" (432 mm. by 559 mm.) This means that one ream of five hundred 17".times.22" sheets of that stock will have a weight of 24 lbs. A similar weight text paper might be a "basis 80" with a sheet size of 25" by 38" (635 mm. by 965 mm.) In each case, the sheets may have different thicknesses so each ream of five hundred sheets has a different height, but each sheet has an effective density of 118 g/m2. That is, in the case of the basis 80 paper, each sheet has an area of 0.61 m2 and a weight of approximately 72.3 g., and a ream of five hundred such sheets would have a weight of approximately 36.15 kg. or 80 lbs. In contrast, a standard cover stock might be basis 100 with a sheet size of 251/2" by 38" (648 mm. by 965 mm.), and have a sheet density of 270 g/m2.
When converting these designations to a standard large sheet size of 32" by 42" (813 mm. by 1067 mm.), it may be seen that a ream of the basis 80 text stock would weigh approximately slightly over 51 kg. or 112 lbs., and a ream of the cover stock would weigh slightly over 117 kg. or 257 lbs. The relative heights of each ream might be the same but are likely to be significantly different from one another.